Context and DFD slides

Report
Context and Data Flow Diagrams
Activity presented by
Coral Shand
March 2012
Scenario
The Car Club has many enthusiastic members.
Prospective members can join the club by sending
in a membership form along with $10. A planning
committee decides on new activities for the coming
month and these are passed on to members in a
monthly newsletter. Information about all activities
past and present are stored for future use.
Members also receive reminder letters when their
membership is due for renewal.
CONTEXT DIAGRAM
Prospective
Member
The Car
Club
Member
Planning
Committee
Information in the scenario
Name the data flows
Membership form
Planned activities
Monthly newsletter
Membership renewal
New member details
Planned activities
Newsletter
Renewal reminder
External Entity
Prospective
member
Data flow IN
(into the system)
• New member
details
• Newsletter
• Renewal
reminder
Member
Planning
committee
Data flow OUT
(out of the system)
• Planned
activities
CONTEXT DIAGRAM
Prospective
Member
The Car
Club
Newsletter
Member
Planning
Committee
New member details
Renewal
Reminder
Planned
activities
Data flow arrows in Context
Diagram
New member details
Newsletter
Renewal Reminder
Planned Activities
Processes for Data Flow
Diagram
Add new member
Add planned activities
Create newsletter
Create renewal reminder
DATA FLOW DIAGRAM
Prospective
Member
Create
newsletter
Add new
member
Create
renewal
reminder
Member
Add
planned
activities
Planning
Committee
Members
Activities
Prospective
Member
DATA FLOW DIAGRAM
Create
newsletter
Add new
member
Activities
Members
Create
renewal
reminder
Member
Add
planned
activities
Planning
Committee
Prospective
Member
DATA FLOW DIAGRAM
New
member
details
Create
newsletter
Add new
member
Member details
Activities
Members
Create
renewal
reminder
Renewal
reminder
Member
Member
details
Add
planned
activities
Planning
Committee
DATA FLOW DIAGRAM
Prospective
Member
Member details
New
member
details
Create
newsletter
Updated
activities
Add new
member
Updated
activities
Member details
Activities
Members
Create
renewal
reminder
Renewal
reminder
Member
Add
planned
activities
Member
details
Newsletter
Planned
activities
Planning
Committee
TEN RULES
1.
2.
3.
4.
An external entity must be an intelligence.
Data flows are labelled with adjective-noun.
Processes are named with a verb-noun.
A data flow arrow coming from a process
cannot have the same name as a data flow
arrow going into that process.
5. Processes and data stores must have at least
one data flow arrow in and one out.
6. A data store cannot link directly to another
data store. An external entity cannot link
directly to another external entity.
7. Data flows from external entity may keep the
same name. Data flowing to and from a data
store must have the same name.
8. Events at same time are one event.
9. Data flow arrows should not cross each other.
10. Do not use words ‘data’ or ‘process’ in label
names.

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